1. Field of the Invention
The invention relates to an apparatus for the manufacture of sheets of corrugated board of variable size, comprising at least one longitudinal cutting arrangement having longitudinal cutters adjustable at right angles to the conveying direction of the nondivided web of corrugated board for cutting sectional webs of corrugated board of differing format width, cutting devices adjustable at right angles to the conveying direction of the web of corrugated board for cutting lateral margins of the web of corrugated board, discharge devices for margins that have been cut off, and at least one cross cutting arrangement for cutting sheets of corrugated board from the sectional webs of corrugated board.
2. Background Art
In an apparatus of the generic type known from U.S. Pat. No. 5,393,294, the at least one longitudinal cutting device is preceded by a cross cutting device for the margins. In the case of a change of size, i.e. in case the longitudinal cutting devices are adjusted to another format width of the sectional webs of corrugated board to be cut, then a cross cut is performed from both sides of the web. To this end, a corresponding cross cutting device is disposed upstream of the at least one longitudinal cutting device--referred to the, conveying direction of the web of corrugated board. The two lateral cross cuts exceed the widest margin to be severed. There is no cross cutting of the complete web upstream of the longitudinal cutting devices. The web of corrugated board can be conveyed without cross cutting in the conveying direction as far as to the cross cutter for the the sheets of corrugated board, the guidance and accurate conveying motion thus being maintained. The cuts of transverse and longitudinal extension are performed precisely and with positional accuracy. The portion of the corrugated board web that has overlapping formats during the change of size is cut out as waste by the cross cutter located at the end of the apparatus and discarded. It is of disadvantage that the margins must be cross cut and led anew into the discharge devices for every change of size, which may cause malfunction, given the high conveying speeds of the web of corrugated board. With this design, the cross cutting device used at the end for cutting the sheets of corrugated board from the sectional webs of corrugated board can only be a simplex cross cutting device, i.e. the individual sectional webs of corrugated board must have the same format length.
If sheets of corrugated board of different format length are to be produced, such an apparatus for the manufacture of sheets of corrugated board of variable size is configured such that--referred to the conveying direction--the at least one longitudinal cutting device is preceded by a cross cutter, by which the corrugated board web is divided over the entire width of the web. The remaining web is accelerated for a certain number of sheets so that a gap forms between the leading web and the following web of corrugated board. For a sufficiently long gap to result, a transfer table of corresponding length must be available between the cross cutter and the at least one longitudinal cutter. When, because of the gap, the leading web of corrugated board has left the longitudinal cutting device and the following web has not yet reached the latter, the longitudinal cutting devices and, if necessary, corrugating devices are adjusted to the new format width or widths, respectively. This has the disadvantage that the corrugated board web following in the conveying direction is not exposed to any traction and, therefore, not sufficiently guided. This may result in inaccuracies of cut by the cross cutter and inaccuracies of cutting by the longitudinal cutting device. Unnecessary waste and possibly malfunction in operation will result. This is especially troublesome with webs of corrugated board which are printed and must be cut true to size. Moreover, the acceleration of the leading web required for the gap to form will cause inaccuracies of cut.